Method of placing a web

ABSTRACT

A method and apparatus for laying a web in a submerged condition on an entrenchment floor includes wrapping a web onto a drum as said drum is floating on a water surface of the entrenchment, navigating the wrapped drum to a beginning section of the entrenchment, and unwinding the drum as it is floating on the entrenchment while further navigating the drum. Water is pumped from a section of the entrenchment already layed with the web, thus imparting an unwinding force to the drum and giving the web a convex shape along the portion of the web which extends from the drum to the entrenchment floor.

BACKGROUND OF THE INVENTION

The invention relates to a method of placing a web on an entrenchmentbelow the ground water level. Usual methods of placing such a webconsist of first draining the entrenchment at the start of aconstriction project so that the web can be placed in a simple way.Draining the water does however also affect the ground water level inthe area outside the entrenchment and therefore, draining is not alwaysallowed at the beginning of a constrication project. A typical exampleis an entrenchment for a road near a wildlife habitat.

SUMMARY OF THE INVENTION

The invention provides a solution for the above problem. According tothe invention, the solution is achieved by wrapping the web around acore or roll, floating the core or roll in either the entrenchment or awater course which is connected with the entrenchment, and subsequentlynavigating the wrapped-up core or roll to the beginning of theentrenchment, after which unwinding and attachment of the web takesplace.

Such a web is preferably formed by connecting lengths of web materialsegments, cut off at size substantially parallel to the center line ofthe core or roll, to preceding lengths of web material segments. The websegments can be connected by welding or adhering.

The length of the core should substantially be equal to the resultantwidth of the entrenchment. If a road is concerned which has to beprocessed in this way, it is determined according to the invention, thatthe resultant width of the entrenchment is realized by enlarging theprojected width by applying at least one flood verge.

Unwinding takes place after the core is positioned by pumping water fromthe entrenchment at the location where the web still has to be applied,to the location between the initial edge of the web and the core. Duringthis pumping, a braking moment and braking force is preferably exertedon the core.

In order to apply the method according to the invention also a number ofinstallations is necessary. The floating core is for instance formed sofor that purpose, that, while being pivotal about its own axis by meansof moment arms, it is connected to at least one pontoon, the pontoonbeing provided with winches to bring the core in the correct position.

Furthermore means are necessary to lower compression means with the aidof guide cables to secure the web edges, provided with ring eyes, tostructure parts, positioned under water. For this purpose, the guidecables extend between screw eyes, present in a concrete clamping edge,to for instance auxiliary scaffolds or one or more derrick barges,dependent upon the nature of the intermediary structures. Preferably,barbed bars are provided between the guide cables and screw eyes.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further elucidated hereinafter on the basis of thedrawings, in which by way of example an embodiment is shown of aninstallation to apply the method according to the invention. In thedrawings:

FIG. 1 an abridged cross-section of an entrenchment having someinstallations at the left adapted to be used when applying the methodaccording to the invention, and having at the right an entrenchmentprofile with a flood verge under the water level, all this substantiallyaccording to the line I--I of FIG. 2;

FIG. 2 shows a schematic plan view of the installations of FIG. 1;

FIG. 3 shows a longitudinal section of an entrenchment at the locationof a part of a structure protruding above the water, to elucidate thebeginning of the web placing process;

FIG. 4 shows details of the guide means of FIG. 3; and

FIG. 5 shows a longitudinal section of an entrenchment at the locationof a structure which does not protrude above the water level, on thebasis of which the end of the web placing process is elucidated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIGS. 1 and 2, the equipment at the left includes a working floor 1having a length which is equal to the resultant width of a web which iswound on a reel 2. The resultant width of the web may be, for example,175 meters. Along the working floor 1, a core 3 can be moored, on whichthe web is wound. This is effected by winding the complete web V,necessary for one section, i.e., a part of the entrenchment between forinstance two structures, including a triangle as a consequence of apossible oblique crossing of one of the structure parts, and theprefabricated web edges. It goes without saying that the entrenchmentneed not be rectangular in plan view, but may have any shape.

The drum is moored as closely as possible against the working floor, andthe working floor may be over a slope 4. The drum 3 can comprise a steeltube having a diameter of approximately 1 meter and a wall thickness ofapproximately 12.5 millimeters. On the other hand, the web is very thin(up to a magnitude of 1 millimeter) by which only an increase in radiusof some tens of centimeters is developed around the drum 3 for anentrenchment of approximately 400 meters. The working floor 1 can belocated in the vicinity of the bank of the section to be dredged or asmall channel which communicates with said section to be dredged.

The drum 3 is connected to two small pontoons 7 via two moment arms,which are connected to the drum via a hydromotor 6. This additionalstructure causes the total width of the roll with pertaining parts to beapproximately 2 meters larger than the length of the core or rollitself. Winches 8 are provided on the pontoons, and the winches 8 arecontrollable both with respect to their tensile force and holding force.With the aid of the winches 8, the core or roll can be introduced intoand maintained in any position within the dredged section.

The initial and final operations when placing the web at the beginningand end of the entrenchment are most simple, as the web needs not bearranged under water in these situations. However, the situation at thelocation of the structures K is completely different, such as structureswhich protrude above the water surface P, as in FIG. 3, and structureswhich do not protrude above the water surface P, as in FIG. 5.

In the event the structure K obliquely intersects the entrenchment, thedrum 3 can be manoeuvered to the extreme corner point of the respectivesection, and then the partly unwound point can be drawn onto anauxiliary scaffold 10 (FIG. 3), secured to a viaduct 9, and temporarilyanchored. By further unwinding the roll and navigating it parallel tothe viaduct 9, the total web edge can be brought onto the auxiliaryscaffold 10. One will note then, that the complete triangle is betweenthe roll and the viaduct in a folded manner, which, however, presents nodisadvantage.

Before the roll or core 3 is navigated against the viaduct 9, spacedapart vertical guide cables 11 are prearranged from screw eyes 13 (FIGS.3 and 4) located in a concrete clamping edge 12, to the auxiliaryscaffold 10 to be arranged. The vertical guide cables 11 can be spacedapproximately 3 meters apart from one another. The guide cables 11 arelaced through ring eyes (not shown) present in the web edge. Furthermorethe web edge is provided with some ballast, with the aid of which theweb edge can be lowered along the guide cables.

A barbed bar 14 is placed between the guide cables 11 and the concreteclamping edge 12 (FIG. 4) which should prevent the web, when passed overthe barbed bar 14 from sliding back. With sensors one can determinewhether the web edge is in the required position and if not, it can bebrought into the required position.

Before the clamping construction 15, weighing about 1 ton, can bearranged, it has to be certain that on its track laong the guide wires11 it does not meet the web V, as this will undoubtedly cause damage. InFIG. 3 two clamping constructions 15 are visible. One clampingconstruction 15 is on an already provided clamping edge 12 of thestructure K. The other clamping construction 15 is shown closer to thewater surface P, and this latter clamping construction will be arrangednext to the first one. Securing the clamping constructions 15 next toeach other takes place by turning nuts 23 (FIG. 4) over the screw eyes13. The guarantee that the web will not be damaged by the clampingconstructions can be achieved by further turning the core or roll in aposition perpendicular to the axis of the entrenchment, keep them undercontrol, and then introducing a slight difference in water pressure bymeans of pumping over water. This exerts a pressure on the web, thepressure being indicated by arrows A in FIG. 3. Care should be taken,however, that the water that flows to create this pressure causes theleast disturbance possible, and that is the reason that, for instance, along spray pipe 34 must be sued for spraying a water spray 35 towardsthe web.

After having checked first whether the web does indeed leave theclamping edge 12 almost horizontally, the clamping units 15, which havea length of approximately 6 meters, can be payed out one by one from theauxiliary scaffold 10 along the guides wires 11 and screwed on with theaid of divers.

The web V can now be further payed out under a certain braking momentand braking force by pumping-over water, while care is furthermore takenthat the core or roll will not become clamped against one of the banks.

It has to be remarked that a leak flow around the core heads or rollheads has an erosive effect. Therefore a light erosion protection of 0.1meters of gravel on the slope is necessary. Furthermore one shouldrealize that the resultant length may be approximately 5 meters longerthan the projected one, which requires the provision of a flood verge,indicated at the right in FIG. 1 by means of a dashed line 16. It isalso possible to solve this problem by including a fold on the core orroll.

In order to ensure that the web edge does not disappear under water, itis advisable to fix it with for instance pegs 17 (FIG. 1), which canthen be connected by wires 22 to a ring eye (not shown), which isincluded in the reinforced web edge.

In a later stage the web edge has to be brought above the water and theflood verge has to be completed. This can be done by locally withdrawingthe web edge from the opposite side of the section of the entrenchmentand thereby enabling re-profiling the verge.

The connection of the web at the ends of the respective sections of theentrenchment takes place in a similar manner as described for theconnection at the beginning at the location of a structure K.

A difference is, however, that a water enclosure 18 (FIG. 5) isintroduced between the web and the bottom, i.e., under the fold, whichcan, however, be discharged by creating an overpressure relative to theground water.

In order to ensure that the fold will be on the bottom, a sausage-likeballast or weight 32, which is connected at one side to the guide wires11, can be lowered parallel to the axis of the entrenchment to createthe above-mentioned overpressure so that the water in the waterenclosure 18 is discharged.

The connection to the structure 19 (FIG. 5), which does not extendthrough the water level, is additionally complicated, so that one has towork from the water with a derrick barge 20. The guide wires 11 can thenbe tensioned by means of somewhat more robust floats 21.

Although the invention is elucidated hereabove on the basis of anapplication to an entrenchment for a road for automobile traffic inwhich the entrenchment is, in fact, required to be drained at some timein the future after the web has been laid, it is remarked that theinvention method and the pertaining installations can also be used insituations where no draining at any point in time is permitted since noinfluence of the ground water level in the direct neighborhood ispermissible. In this respect one may think of large closed reservoirs,like rubbish tips, water basins, swimming pools and the like reservoirs.

We claim:
 1. A method for laying a web in a submerged condition on anentrenchment, comprising the steps of:forming a web by joining sectionsof web material lengths together along edges extending substantiallyparallel to a center axis of a drum; winding said web onto said drum assaid drum is floating on a fluid surface; navigating and floating saidwound drum to a beginning section of said entrenchment to be laid;unwinding said would drum while further navigating and floating saiddrum along a water surface of said entrenchment; pumping water in saidentrenchment from a section of said entrenchment where said web has notbeen laid to a section of said entrenchment between said beginningsection of said entrenchment and said floating drum to decrease a radiusof curvature of a convex surface of said web to aid in unwinding saidweb from said floating drum, said convex surface extending from saiddrum to a floor of said entrenchment; and a longitudinal axis of saiddrum being substantially parallel to said fluid surface as said drum iswound and said axis being substantially parallel to said water surfaceas said drum is navigated, floated and unwound.
 2. The method claimed inclaim 1 further comprising the step of:exerting a braking moment andbraking force on said floating drum while pumping said water.
 3. Themethod claimed in claim 1 wherein a hydrometer is used for unwindingsaid drum.
 4. An apparatus for laying a web in a submerged condition onan entrenchment comprising:a floating drum; a web formed by joiningsections of web lengths together along edges extending substantiallyparallel to a center axis of said drum, said web being wound onto saidfloating drum as said drum is floated on a water surface; means fornavigating and floating said wound drum to a beginning section of saidentrenchment to be laid; means for unwinding said wound drum whilefurther navigating and floating said drum along said water surface ofsaid entrenchment; means for pumping water in said entrenchment from asection of said entrenchment where said web has not been laid to asection of said entrenchment between said beginning section of saidentrenchment and said floating drum to decrease a radius of curvature ofa convex surface of said web to aid in unwinding said web from saiddrum, said convex surface extending from said drum to a floor of saidentrenchment; and a longitudinal axis of said drum being substantiallyparallel to said water surface as said drum is wound and said axis beingsubstantially parallel to said water surface as said drum is navigated,floated and unwound.
 5. The method claimed in claim 4 wherein saidunwinding means and said navigating means comprises at least onepivotable moment arm connected to said drum for rotating said drum;atleast one pontoon connected to said at least one pivotable moment arm;and at least one winch secured to said at least one pontoon fornavigating said drum.
 6. The apparatus claimed in claim 5 wherein alength of said drum is substantially equal to a width of saidentrenchment.
 7. The apparatus claimed in claim 4 or 5 wherein saidunwinding means further comprises a hydrometer.